The invention concerns auxiliary or supplementary means for driving the feeder conveyors of a mobile harvester and more particularly means for driving them in reverse for the purpose of clearing blockages.
Selectively operable reverse drives for various conveyors of harvesting machines, including those of a header of a combine, are well known. Their principal use is in assisting an operator to clear crop material or foreign bodies when the feeding system becomes plugged or jammed during harvesting operation. Typically, the reverse drive is engaged sufficiently to "back up" some of the wedged material so that an operator can remove it by hand and/or redistribute it so that it can be handled by normal forward operation of the conveyor.
Ideally, a reversing system should be safe and convenient to use, effective and reliable in operation, use simple components and controls be relative1y low in cost. Ready adaptability of a basic system to a variety of harvesters is of course a cost factor. Known reversers fall short of this ideal in one respect or another.
Although reverser arrangements have wide applicability in harvesting machines, for convenience, the fo11owing discussion will be confined to the exemplary embodiment of the combine harvester.
Love's reverser (U.S. Pat. No. 4,138,837, also assigned to the assignee of the present invention) makes use of a reversible planetary gear drive in a combine header transmission. The arrangement is functionally good -- Love takes advantage of the gear transmission to provide a reduced speed, high torque reverse mode and avoidance of simultaneous engagement of forward and reverse is inherent in the arrangement -- and on a self-propelled combine, proximity of the operator's station makes use of a simple mechanical or cable control feasible. However, although highly reliable, the system is relatively expensive and 1ess attractive for a pull-type combine where the operator's station (of the towing tractor) is quite remote from the feederhouse of the combine where the reversible gear transmission is normally mounted.
In the Love arrangement, the regular combine mechanical power train and drive input is used to power the reverser but in another approach, exemplified by Richards (Successful Farming, June-July 1983, page 31) the reverser power source is an electric motor carrying a pinion engaging a ring gear on a drive shaft of the header. This is a relatively simple system of moderate cost in its self-propelled combine application. However, it is less attractive for the pull-type combine application because of problems of electrical power transmission over the relatively long distance between the electrical power source on the towing tractor and the electric motor on the header.
Droningborg (advertisement, Power Farming, April 1984, page 228) and Tourdot (U.S. Pat. No. 4,430,847) both use electrohydraulic systems for header reversers with a hydraulic motor as the drive actuator in both cases. Use of an auxiliary hydraulic motor as the reverse drive actuator offers advantages over a mechanical (gear) reversible drive forming an integral part of the regular forward drive system of the header conveyors but the potential advantages are not fully realized in Tourdot. The hydraulic motor is interposed at a point in the conveyor drive system which requires that the whole header be driven in reverse through the drive belt of one of its component parts (the upper conveyor portion) requiring that this drive section be adequate for its double duty. Tourdot upgrades this drive section for the reverse drive requirement, in part by adding the cost and complication of means for automatically adjusting a belt idler when the reverse drive mode is selected. In addition, Tourdot uses an automatic clutch which, at least when used in combination in a commercial embodiment of his invention, requires that the operator, in changing from the reverse mode to forward mode of the header drives, waits for "at least seven seconds" before engaging forward drive so as to avoid damaging the automatic clutch (Operator's Manual Allis-Chalmers Gleaner N5, N6, and N7 Self-Propelled Combines, Oct. 1983, page 58).